Research On Relay Cache And Forwarding Strategy For 6LoWPAN Based On Mesh-under Routing

Since the establishment of 6LoWPAN, a lot of attention from the industry and academia has been drawn to its development. In terms of the architecture, 6LoWPAN has an adaptation layer, so it could transmit the IPv6 packets based on the IEEE 802.15.4 standard or other low power consumption link. Currently, the fragmentation reassembly and header compression techniques of the 6LoWPAN adaptation layer have the relevant standards, and the routing scheme has gradually been improved. With the further development of the techniques, the cache and computing power of the 6LoWPAN node have been improved, but there is still a serious problem that the high-speed data transmission causes the less reliability. In 6LoWPAN, the selection of the suitable intermediate nodes, the cache and retransmission of the data fragmentations will be a future research direction.Firstly, the research background, application scenarios and research status of 6LoWPAN are surveyed. Furthermore, thesis presents the 6LoWPAN technology, the 6LoWPAN routing mechanism and the cache strategies of WSN. And it emphatically describes the 6LoWPAN adaptation layer technology, the Mesh-under routing scheme and the WSN's relay cache and cache management policy.Secondly, in light of the problem that the energy consumption and delay of the end-to-end retransmission based on Mesh-under are more, a cache and retransmission mechanism based on the intermediate nodes is proposed. According to the forwarded data fragmentation information and the node state, the cache situation of data fragmentation is decided, as well as the node's retransmission cache is effectively managed. Thus, the retransmission procedure of the data fragmentation is completed. Simulation results show that the mechanism could improve the destination node's reassembly successful rate and the network's energy utility value.Thirdly, as the data fragmentations are cached and retransmitted based on the intermediate nodes, it could cause the nodes' retransmission cache overflow and the network's performance degradation. So an auxiliary cache mechanism based on Mesh-under is proposed. According to the retransmission cache usage of the nodes on the transmission path and the remaining hop count of the data fragmentation, the mechanism could set the dynamic retransmission cache threshold, and then select a suitable auxiliary cache node from the neighbor nodes of the relay node. Thus, it could complete the data fragmentation's cache and retransmission procedure. Simulation results show that the proposed mechanism can effectively avoid the retransmission cache overflow, substantially reduce the energy consumption and transmission delay, and further improve the destination node's reassembly successful rate.Lastly, the research works are concluded, and the future works are presented.